The present invention relates a technique for controlling an acoustic quality of sound coming from outside a room (or outside a vehicle) into the room (or vehicle).
Japanese Patent No. 2755094 discloses a technique for alleviating a cooped-up feeling which may be felt by a person present in a sound-insulated, soundproof chamber. According to the technique disclosed in the No. 2755094 patent, the soundproof chamber is provided within a room, and one or both of an outdoor microphone provided outside the room and an indoor microphone provided outside the soundproof chamber within the room are selected, through operation on an operation section, so that sound signals picked up by the selected microphone or microphones are audibly reproduced or sounded via a speaker provided within the soundproof chamber.
However, while the person in the room may feel a cooped-up feeling if sound propagated from outside the room (i.e., outdoor sound) is completely blocked by walls etc., the person may feel noisy if sound from outside the room is heard with an original (i.e., unchanged) acoustic quality. With a sound signal processing system including a microphone and a speaker, an outdoor sound can be made to be heard as sound of an acoustic quality suiting a preference of the person; in this case, however, a power supply is required, so that a necessary apparatus construction would increase in size.